Ординатура / Офтальмология / Английские материалы / Optics Retinoscopy and Refractometry_Lens_2005

Astigmatism With Glasses

PLUS CYLINDER a. Gross Spheres

1a

NW: –2.50 + 2.25 x 178 VA c 20/60

Go to 2a.

2a

1a

–2.50 + 2.25 x 178

Chart is on 20/60, which the pt reads with a few misses. To begin with gross spheres, you offer 0.50 of plus first:

–2.00 + 2.25 x 178

Ask, “Is this better (pause) or worse?”

a.Pt says this is more clear; go to 3a.

b.Pt says this is more blurred; go to 4a.

3a

2a

–2.00 + 2.25 x 178

Pt has accepted 0.50 more plus. You wonder how much more plus the pt will take. So you offer another +0.50:

–1.50 + 2.25 x 178

And ask, “Is this more clear . . . or blurry?”

a.Pt says this is more clear; go to 5a.

b.Pt says this is more blurred; go to 6a.

4a

2a

–2.00 + 2.25 x 178

Pt says addition of 0.50 has blurred the chart, so you return to:

–2.50 + 2.25 x 178 then try 0.50 of minus:

–3.00 + 2.25 x 178

and ask, “Is this more clear . . . or blurry?”

a.Pt says more clear; go to 7a.

b.Pt says they look about the same; go to 8a.

5a

3a

–1.50 + 2.25 x 178

Pt has accepted yet more plus. You are dubious but wisely offer yet another +0.50:

–1.00 + 2.25 x 178

a.Pt says this is about the same; go to 9a.

b.Pt says this has blurred; go to 10a.

6a

3a

–1.50 + 2.25 x 178

Addition of 0.50 more plus sphere has caused the chart to blur. You realize you have passed the maximum plus that the pt can accept. You return to the previous setting:

–2.00 + 2.25 x 178

and ask the pt to read the smallest line of letters possible. The pt reads 20/30. You are ready to begin checking the astigmatism.

Go to 15a.

7a

4a

–3.00 + 2.25 x 178

The pt has asked for more minus. Since you are cautious about handing out minus, you ask the pt to read the smallest letters possible.

a.Pt still reads 20/60; go to 11a.

b.Pt reads 20/30; go to 12a.

8a

4a

–3.00 + 2.25 x 178

The pt says that the addition of 0.50 more minus does not really change the clarity of the chart. You want to push as much plus as possible and restore the +0.50:

–2.50 + 2.25 x 178

Gross spheres has produced no change from the starting Rx. You are ready to begin checking the astigmatism.

Go to 16a.

9a

5a

–1.00 + 2.25 x 178

Pt has accepted another +0.50 plus, stating that the chart has not changed. You are dubious but want to give as much plus as possible. So you offer yet another +0.50:

–0.50 + 2.25 x 178

which the pt says is blurry. You know you have pushed as much plus as possible and return to the previous setting:

–1.00 + 2.25 x 178

You now ask the pt to read the smallest letters possible.

a.Pt still reads 20/60; go to 13a.

b.Pt reads 20/30; go to 14a.

10a

5a

–1.00 + 2.25 x 178

Pt states last addition of 0.50 has blurred the chart. You know you have pushed as much plus as possible and return to the previous setting:

–1.50 + 2.25 x 178

You now ask the pt to read the smallest letters possible, and the pt reads 20/40. You are ready to begin checking the astigmatism.

Go to 15a.

11a

7a

–3.00 + 2.25 x 178

The pt can read no better now than with the pt’s original Rx . . . gross changes in sphere have not improved the pt. You want to leave the pt with the maximum amount of plus possible and return to your original reading:

–2.50 + 2.25 x 178

You are ready to check the pt’s astigmatism. Go to 16a.

12a

7a

–3.00 + 2.25 x 178

The pt’s vision has improved substantially, but it is still not 20/20. Adding more minus fails to improve the pt’s vision further. You are ready to check the pt’s astigmatism.

Go to 15a.

13a

9a

–1.00 + 2.25 x 178

The pt has taken a large change in sphere yet shows no improvement. You are suspicious and decide to try –0.50 again:

–1.50 + 2.25 x 178

Now the pt says this is clearer, and the pt proves it by reading 20/40. You are ready to check the pt’s astigmatism.

Go to 15a.

–1.00 + 2.25 x 178

Pt has made a substantial improvement in acuity although it required a sizable addition of plus. You are ready to check the pt’s astigmatism.

Go to 15a.

15a

You have completed the gross spheres step with a reasonable amount of change and a reasonable improvement in vision. You now have several options:

a.Move on to Refine Cylinder Axis Exercise b, PLUS CYLINDER; go to 1b.

b.Start this Exercise again, and choose different options; go to 1a.

16a

You have completed the gross spheres step although the pt’s vision has not improved. You still hope to increase the pt’s acuity by working with the cylinder axis and power. You now have several options:

a.Move on to Refine Cylinder Axis Exercise b, PLUS CYLINDER; go to 1b.

b.Start this Exercise again, and choose different options; go to 1a.

+Astigmatism With Glasses

PLUS CYLINDER b. Refine Cylinder Axis

1b

Beginning Rx: –2.50 + 2.25 x 178

After gross spheres (for a common starting place):

–2.00 + 2.25 x 178

Suppose the pt has read 20/30 with this MR. You now want letters that you know the pt can see easily and put the 20/50 line up. You swing the cross cylinder into place and align the turnstile with the axis. The white dot is counterclockwise to 178, and the red dot is clockwise. You tell the pt, “You are looking at the letters through glass #1 right now. Which seems better, #1 here . . . (pause, then flip cross cylinder over) . . . or this #2?”

a.Pt says #1 is better; go to 2b.

b.Pt says #2 is better; go to 4b.

c.Pt says they are about the same; go to 6b.

2b

1b

–2.00 + 2.25 x 178

Pt says #1 is clearer. You turn the cross cylinder back to choice #1 and note that the white dot is counterclockwise to 178. So, you rotate the axis 15 degrees counterclockwise toward the white dot:

–2.00 + 2.25 x 013

The white dot is still counterclockwise to 013. You say, “Which is clearer now . . . this #3. . .

(pause, flip) . . . or #4?”

a.Pt says #4; go to 3b.

b.Pt says they are about the same; go to 7b.

3b

2b

–2.00 + 2.25 x 013

The pt has chosen #4, with the white dot clockwise to 013. Thus, you will move back toward the axis that you originally came from. You rotate this axis clockwise halfway between 013 and 178:

–2.00 + 2.25 x 006

The white dot is now clockwise to 006. You ask the pt, “Which is better here . . . this #5 that you are looking at now . . . (pause, flip) . . . or this #6?” Pt says they look the same. You are through with axis and ready to check cylinder power.

Go to 9b.

4b

1b

–2.00 + 2.25 x 178

Pt has chosen #2, in which the white dot is clockwise to 178. You rotate toward the white dot 15 degrees clockwise:

–2.00 + 2.25 x 163

The white dot is still clockwise to 163. You say, “Which is clearer now . . . this #3 . . . (pause, flip) . . . or #4?”

a.Pt says #4; go to 5b.

b.Pt says they are about the same; go to 8b.

5b

4b

–2.00 + 2.25 x 163

The pt has chosen #4, with the white dot counterclockwise to 163. This is back toward the direction you originally came from. You rotate the axis counterclockwise halfway between 163 and 178:

–2.00 + 2.25 x 171

The white dot is still counterclockwise to 171. You ask the pt. “Which is better here . . . this #5 that you are looking at now . . . (pause, flip)

. . . or this #6?” The pt hesitates. You realize that this probably means that #5 and #6 look about the same. So you ask, “Or do they look about the same?” Pt says they look the same. You are through with axis and ready to check cylinder power.

Go to 9b.

6b

1b

–2.00 + 2.25 x 178

Pt has said both choices look the same. You realize that this indicates that the axis is now correct, and you are ready to check cylinder power.

Go to 9b.

7b

2b

–2.00 + 2.25 x 013

Pt has said both choices look the same. You realize that this indicates that the axis is now correct, and you are ready to check cylinder power.

Go to 9b.

8b

4b

–2.00 + 2.25 x 163

Pt has said both choices look the same. You realize that this indicates that the axis is now correct, and you are ready to check cylinder power.

Go to 9b.

+Astigmatism With Glasses

PLUS CYLINDER

c. Refine Cylinder Power

1c

Beginning Rx: –2.50 + 2.25 x 178, VA c 20/60 After gross spheres:

–2.00 + 2.25 x 178, VA c 20/30

After refining cylinder axis (for a common starting place):

–2.00 + 2.25 x 171

You are now ready to check cylinder power. You rotate the cross cylinder so that the “P” is in line with the axis. To help you keep your place, each choice is followed by a “W” for the white dot or an “R” for the red dot . . .

whichever is showing at “P.” You ask, “Which is clearer now . . . this #7(W) . . . (pause, flip).

. . or #8(R)?”

a.Pt says #7 is better; go to 2c.

b.Pt says #8 is better; go to 6c.

c.Pt says they are about the same; go to 12c.

2c

1c

–2.00 + 2.25 x 171

Pt says #7, when the white dot appeared, is clearer. You realize this means you should add some more PLUS cylinder power. You give 0.50:

–2.00 + 2.75 x 171

You flip the cross cylinder so that the white dot is again on “P” and ask, “Which is clearer here . . .#9(W) . . . (pause, flip) . . . or #10(R)?”

a.Pt says #10; go to 3c.

b.Pt says they are about the same; go to 11c.

3c

2c

–2.00 + 2.75 x 171

Pt has chosen red dot this time, so you know you should reduce the cylinder power. You remove 0.25, which is half of the 0.50 that you added in the last step:

–2.00 + 2.50 x 171

The red dot is still up. You ask, “Which is better now . . . this #11(R) . . . (pause, flip) . . . or #12(W)?”

a.Pt says #11 is better; go to 4c.

b.Pt says they are about the same; go to 5c.

4c

3c

–2.00 + 2.50 x 171

Pt has again chosen the red dot. You remove another 0.25, which returns you to your starting point:

–2.00 + 2.25 x 171

That is fine. The pt would probably continue to go back and forth between +2.25 cyl and +2.50 cyl all day. You want the pt to have the least amount of cylinder possible. You are now ready for fine spheres.

Go to 13c.

5c

3c

–2.00 + 2.50 x 171

The pt says that the lenses look the same. You realize you have reached your end point and are ready for fine spheres.

Go to 13c.

6c

1c

–2.00 + 2.25 x 171

The pt has chosen #8, with the red dot showing at “P.” You realize this means you should reduce the cyl power. You take out 0.50:

–2.00 + 1.75 x 171

The red dot is still on “P.” You ask, “Which is clearer now . . . this #9(R) . . . (pause, flip) . . .

or #10(W)?”

a.Pt chooses #10; go to 7c.

b.Pt says they are about the same; go to 10c.

7c

6c

–2.00 + 1.75 x 171

The pt has chosen #10, with the white dot at “P.” You know you should restore some of the cyl power you took out previously. You add back 0.25, which is half of the 0.50 that you took out before:

–2.00 + 2.00 x 171

The white dot is still at “P.” You ask, “Which seems better now . . . this #11(W) . . . (pause, flip) . . . or #12(R)?”

a.Pt chooses #11; go to 8c.

b.Pt says they are the same; go to 9c.

8c

7c

–2.00 + 2.00 x 171

The pt has requested another addition of cyl power. You give another 0.25, which returns you to your starting point:

–2.00 + 2.25 x 171

That is fine. The pt would probably continue to go back and forth between +2.00 cyl and +2.25 cyl all day. You want the pt to have the least amount of cyl possible. You are ready for fine spheres.

Go to 13c.

9c

7c

2.00 + 2.00 x 171

The pt says that the lenses look the same. You realize you have reached your end point and are ready for fine spheres.

Go to 13c.

10c

6c

–2.00 + 1.75 x 171

The pt says that the lenses look the same. You realize you have reached your end point and are ready for fine spheres.

Go to 13c.

–2.00 + 2.75 x 171

The pt says that the lenses look the same. You realize you have reached your end point and are ready for fine spheres.

Go to 13c.

12c

1c

–2.00 + 2.25 x 171

The pt says that the lenses look the same. You realize you have reached your end point and are ready for fine spheres.

Go to 13c.

13c

You have completed the Refine Cylinder Power step and now have several options:

a.Continue this refractometric measurement into Fine Spheres Exercise d, PLUS CYLINDER; go to 1d.

b.Start this Exercise over, choosing different options; go to 1c.

c.Refry your beans for the Mexican dinner you are planning.

+Astigmatism With Glasses

PLUS CYLINDER d. Fine Spheres

1d

Beginning Rx: –2.50 + 2.25 x 178, VA c 20/60 After gross spheres:

–2.00 + 2.25 x 178, VA c 20/30 After refining cylinder axis: –2.00 + 2.25 x 171

After refining cylinder power (for a common starting place):

–2.00 + 2.25 x 171

You are now ready to check for fine spheres. You rotate the cross cylinder out of the way. Now it is time to see if the cylinder changes you made helped the pt’s acuity, so you ask the pt to read the smallest letters possible.

a.Pt reads 20/25; go to 2d.

b.Pt reads 20/40; go to 5d.

2d

1d

–2.00 + 2.25 x 171

Pt has read 20/25. You now begin the fine spheres stage by offering 0.25 more plus (always offer plus first):

–1.75 + 2.25 x 171

and ask, “Can you see the letters any better now?”

a.Pt says they are about the same; go to 3d.

b.Pt says letters are a bit blurred now; go to 15d.

c.Pt says letters are a bit clearer; go to 16d.

3d

2d, 14d

–1.75 + 2.25 x 171

The pt says the letters are about the same. You still want to give the most plus you can and offer an additional 0.25:

–1.50 + 2.25 x 171

The pt reports this has blurred the chart, so you take the 0.25 back out:

–1.75 + 2.25 x 171

Your refractometric measurement is complete. Now is the time to urge your pt to read the smallest letters possible.

a.Pt reads 20/30; go to 4d.

b.Pt reads 20/20; go to 17d.

4d

3d

–1.75 + 2.25 x 171

The pt does not read as well now as when you started the fine spheres test. Although the pt said that the letters seemed the same in frame 2d, something is amiss. You try going back 0.25 again:

–2.00 + 2.25 x 171

Pt now reads 20/20–. You are through! Final MR: –2.00 + 2.25 x 171

VA c 20/20– Go to 22d.

5d

1d

–2.00 + 2.25 x 171

The pt reads less now than before you checked the pt’s astigmatism. Before moving into fine spheres, you want to know if the change in astigmatic correction caused the decrease in acuity. With the pt looking at the 20/40 letters, you ask, “Are the letters more clear like they are now . . . (pause, then turn the axis back to 178 degrees) . . . or here?”

–2.00 + 2.25 x 178

a.Pt notes no difference; go to 6d.

b.Pt says letters are clearer now; go to 13d.

c.Pt detects slight blur now; go to 14d.

6d

5d

–2.00 + 2.25 x 178

The pt says the letters look the same at axis 171 as 178. You like to change things as little as possible, so you leave the refractor at this setting and ask the pt to read again. The pt manages 20/30. You now move into fine spheres and start by offering 0.25 more plus (always try plus first):

–1.75 + 2.25 x 178

a.Pt says this is better; go to 7d.

b.Pt says this is about the same; go to 12d.

7d

6d, 13d

–1.75 + 2.25 x 178

Pt says the addition of 0.25 more plus is clearer. You want to give the maximum amount of plus possible, so you offer yet another 0.25:

–1.50 + 2.25 x 178

The pt reports that this has blurred the chart, so you take the 0.25 back out:

–1.75 + 2.25 x 178

Your refractometry is finished. Now, you want the pt to read the smallest letters possible.

a.Pt reads 20/30; go to 8d.

b.Pt reads 20/20; go to 11d.

8d

7d

–1.75 + 2.25 x 178

The pt reads no better now than when you started fine spheres. Just to be sure, you take out the 0.25:

–2.00 + 2.25 x 178

and ask again, “Is this still about the same?”

a.Pt says this is better; go to 9d.

b.Pt says about the same; go to 10d.

9d

8d

–2.00 + 2.25 x 178

Pt now says this is better. So you push the pt to read the smallest letters possible. The pt reads 20/20–. You are through!

Final MR: –2.00 + 2.25 x 178 VA c 20/20–

Go to 22d.

10d

8d

–2.00 + 2.25 x 178

Pt says this is still the same. Since you want to push plus, you restore the 0.25:

–1.75 + 2.25 x 178

and ask the pt to read one more time. The pt reads 20/25–. You are through!

Final MR: –1.75 + 2.25 x 178 VA c 20/25–

Go to 22d.

–1.75 + 2.25 x 178

Pt has read 20/20, so you are finished! Final MR: –1.75 + 2.25 x 178

VA c 20/20

Go to 22d.

12d

6d, 13d

–1.75 + 2.25 x 178

The pt says the letters are about the same. You still want to give the most plus you can and offer an additional 0.25:

–1.50 + 2.25 x 178

The pt reports this has blurred the chart, so you take the 0.25 back out:

–1.75 + 2.25 x 178

You are almost through! You urge the pt to read the smallest letters possible. The pt reads 20/20–.

Final MR: –1.75 + 2.25 x 178

VA c 20/20–

Go to 22d.

13d

5d

–2.00 + 2.25 x 178

The pt maintains that the pt’s original axis is clearer than that found in the refining axis step. You have the pt prove it by asking him or her to read smaller letters on the chart. The pt reads 20/30. You now move into fine spheres. You start by offering 0.25 more plus (always try plus first):

–1.75 + 2.25 x 178

a.Pt says this is better; go to 7d.

b.Pt says this is about the same; go to 12d.

–2.00 + 2.25 x 178

The pt says that the letters are a bit blurred now. So you return to the axis of 171:

–2.00 + 2.25 x 171

and urge the pt to read again. This time, the pt manages 20/30. You now begin fine spheres by offering 0.25 more plus (always offer plus first):

–1.75 + 2.25 x 171

and ask, “Are the letters any clearer now?”

a.Pt says letters are a bit blurred now; go to 15d.

b.Pt says letters are about the same; go to 3d.

15d

2d, 14d

–1.75 + 2.25 x 171

The pt says the letters are blurred now, so you know you have pushed beyond the maximum plus. You remove the 0.25:

–2.00 + 2.25 x 171

Now try –0.25:

–2.25 + 2.25 x 171

The pt says this is no better. Since there was no improvement and you want to give the most plus you can, you restore the 0.25:

–2.00 + 2.25 x 171

and urge the pt to read the smallest letters possible. The pt reads 20/25+. You are through! Final MR: –2.00 + 2.25 x 171

VA c 20/25+ Go to 22d.

16d

2d

–1.75 + 2.25 x 171

Pt has said the letters are clearer. You want to give the maximum amount of plus possible, so you offer yet another 0.25:

–1.50 + 2.25 x 171

a.Pt says this is blurred; go to 18d.

b.Pt says this is about the same; go to 19d.

17d

3d

–1.75 + 2.25 x 171

The pt has read 20/20 with the above measurement. You are through!

Final MR: –1.75 + 2.25 x 171 VA c 20/20

Go to 22d.

18d

16d

–1.50 + 2.25 x 171

The pt says the letters are blurred now, so you know you have pushed beyond maximum plus. You remove the 0.25:

–1.75 + 2.25 x 171

and urge the pt to read the smallest letters possible. The pt reads 20/20. You are finished! Final MR: –1.75 + 2.25 x 171

VA c 20/20 Go to 22d.

19d

16d

–1.50 + 2.25 x 171

Pt says the letters look about the same. You still want to give the most plus you can and offer an additional 0.25:

–1.25 + 2.25 x 171

The pt reports this has blurred the chart, so you take the 0.25 back out:

–1.50 + 2.25 x 171

Now you urge the pt to read the smallest letters possible.

a.Pt reads 20/20–, go to 20d.

b.Pt reads 20/30–, go to 21d.

20d

19d

–1.50 + 2.25 x 171

You are through!

Final MR: –1.50 + 2.25 x 171 VA c 20/20–

Go to 22d.

21d

19d

–1.50 + 2.25 x 171

The pt does not read as well as before you started the fine spheres test. Although the pt thought the letters seemed clearer in frame 16d, something is wrong. You try going back 0.25 again:

–1.75 + 2.25 x 171

Now the pt again reads 20/25+. You are through!

Final MR: –1.75 + 2.25 x 171 VA c 20/25+

Go to 22d.